Correctly implements RFC6531

[j-bernard]

Symfony version(s) affected

5.1

Description

Commit d057dff allows non-ASCII local-part in email addresses but this should come with RFC6531 implementation (SMTPUTF8 extension).
It seems that this is not implemented.

How to reproduce

$transport = new EsmtpTransport($host, $port);
$mailer = new Mailer($transport);

$email = (new Email())
    ->from($from)
    ->to($to)
    ->subject($subject)
    ->text($recipient);
$mailer->send($email);

If you try sending an email with non-ASCII email address to a server that correctly implements RFC6531, it will return 501 Syntax Error.
You can try with this version of Mailhog that implements SMTPUTF8 extension.

Possible Solution

Implement RFC6531

Additional Context

No response

[carsonbot]

Hey, thanks for your report!
There has not been a lot of activity here for a while. Is this bug still relevant? Have you managed to find a workaround?

[j-bernard]

This is still relevant! There is no way to make this work without fixing the library.
The implementations is not following the RFC standard.

[stof]

@j-bernard but are you willing to contribute a fix ?

[j-bernard]

I'm willing but the real question is do I have the time to work on it ;)
I'll keep you in touch whenever I start working on this, I have no idea of the complexity of this as it will certainly depend on how the SMTP client is implemented. In the meantime, f you guys are interested in fixing this I can still provide some help and guidance.

[fabpot]

Swiftmailer has SMTPUTF8 support, but it comes with some constraints. So, I decided to not port it to Symfony Mailer as converting the domain to ASCII is enough to make it work everywhere.
Closing for now.